/Engine/Plugins/Online/OnlineSubsystem/Source/Public/Interfaces/OnlinePartyInterface.h
Promote a user from an existing party to be admin All existing party members notified of promoted member (see FOnPartyMemberPromoted)
true if task was started
bool PromoteMember ( const [FUniqueNetId](API\Runtime\CoreOnline\Online\FUniqueNetId) & LocalUserId, const [FOnlinePartyId](API\Plugins\OnlineSubsystem\FOnlinePartyId) & PartyId, const [FUniqueNetId](API\Runtime\CoreOnline\Online\FUniqueNetId) & TargetMemberId, const [FOnPromotePartyMemberComplete](API\Plugins\OnlineSubsystem\Interfaces\FOnPromotePartyMemberComplete) & Delegate )